Solar grain drying system and method

ABSTRACT

The invention includes an apparatus, system, and method for the drying of particulate agricultural matter, especially particulate crops, such grains. The present invention provides a crop particulate (i.e., grain) drying system utilizing solar energy to heat a heat transfer fluid or solution within concomitant forced-air and radiant heat systems which pass heated air through a crop particulate material contained within a conventional crop silo or bin. Electricity demand may be met through utilization of solar photovoltaic panels backed up by connection to an external power source (i.e. power utility).

RELATED APPLICATION DATA

This application is a divisional of U.S. application Ser. No.12/792,185, filed Jun. 2, 2010, now U.S. Pat. No. 8,561,315, which isincorporated herein in its entirety by reference.

TECHNICAL FIELD

The present invention relates generally to grain drying systems andmethods of grain drying structure utilizing solar energy.

BACKGROUND OF THE INVENTION

The present invention relates generally to grain drying structures andmore particularly to grain drying structures and systems utilizing solarenergy.

It is desirable to be able to dry grain efficiently and relativelyquickly, rather than rely upon drying in the fields which often achievesvaried and unpredictable results, and carries with it the risks ofadverse weather conditions that may cause rot or keep the farmer fromharvesting the grain as desired.

Typically, grain may be dried in silos using typical ventilation anddrying arrangements with propane used to heat the drying air flow thatis circulated through the grain, often accompanied by agitation.However, propane is very expensive and often serves as an economicdeterrent to silo drying. Accordingly, there remains a need for solargrain drying systems that make efficient use of solar energy while beingcapable of continuous operation of the system as solar output varieswithin a treatment cycle.

Further, there is a need for grain drying equipment utilizing all theadvantages of other energy sources while being adapted to be used incombination with solar heat as the source of energy.

It is also desirable to provide a silo system for use in grain dryingthat better maintains the temperature of the drying air so as to makethe drying process more uniform and less susceptible to changes inground temperature or other weather conditions.

The present invention represents an improvement over prior art apparatusand methods, such as those described in U.S. Pat. Nos. 3,919,784;3,979,838; 4,045,880; 4,109,395; 4,169,459; 4,198,956; 4,253,244;4,285,143; 4,368,583; 4,391,046; 4,524,528; 5,557,859; 5,028,299;6,209,223; 6,167,638; 7,240,029; 7,461,466; 7,434,332; and 7,263,934,and in U.S. Published Patent Applications Serial Nos. 20040060250,20040154184, 20060111035, 20060123655, 20060130357, 20070234587, and20090094853, all of which are hereby incorporated herein by reference.The present invention may be used in accordance with such prior artsystems and methods.

The present invention addresses remaining needs in the art including theefficient use of energy in solar grain drying, and provides benefits inthe form of more uniform temperature in the drying air flow.

SUMMARY OF THE INVENTION

In general terms, the present invention includes a system and method forthe drying of particulate agricultural matter, especially particulatecrops, such as grains.

Silo Grain Drying System with Alternative Heat Transfer Fluid Sources

The present invention includes a system for drying a particulateagricultural product in a silo, the system comprising: (a) a silo havingan interior space, the silo comprising an air conduit adapted to providedrying air to the interior space;(b) an air blower adapted to provideforced air into the air conduit; (c) at least one heat exchanger in heattransfer contact with the air conduit, the heat exchanger adapted toaccept a heat transfer fluid; (d) a heat transfer fluid storage tankadapted to accept and store a heat transfer fluid, and to supply theheat transfer fluid to the heat exchanger; (e) an evacuated tube solarpanel adapted to heat a heat transfer fluid and to supply the heattransfer fluid alternatively to the heat exchanger and to the heattransfer fluid storage tank; (f) a photovoltaic solar panel adapted togenerate electricity and to supply electricity to the heat transferfluid storage tank; (g) a heating unit adapted to heat the heat transferfluid in the heat fluid storage tank, the heating unit adapted to useelectricity generated by the photovoltaic solar panel; and (h) anoptional controller unit adapted to determine whether the heat transferfluid supplied to the heat exchanger by the evacuated tube solar panelis at a temperature insufficient to maintain the forced air at apre-determined temperature, and in such event to signal the heattransfer fluid storage tank to supply the heat transfer fluid to theheat exchanger.

In another embodiment, the present invention includes a system fordrying a particulate agricultural product in a silo, the systemcomprising (a) a silo having an interior space, the silo comprising anair conduit adapted to provide drying air to the interior space; (b) anair blower adapted to provide forced drying air through the air conduit;(c) at least one heat exchanger in heat transfer contact with the airconduit, the heat exchanger adapted to accept a heat transfer fluid; (d)a heat transfer fluid storage tank adapted to accept and store a heattransfer fluid, and to supply the heat transfer fluid to the at leastone heat exchanger and to receive the heat transfer fluid from the atleast one heat exchanger; (e) an evacuated tube solar panel adapted toheat a heat transfer fluid and to supply the heat transfer fluid to theheat transfer fluid storage tank and to receive the heat transfer fluidfrom the heat transfer fluid storage tank; (f) a photovoltaic solarpanel adapted to generate electricity and to supply electricity to theheat transfer fluid storage tank; (g) a heating unit adapted to heat theheat transfer fluid in the heat fluid storage tank, the heating unitadapted to use electricity generated by the photovoltaic solar panel;(h) a silo air sensor adapted to determine whether the drying air is ata pre-determined temperature; and (i) a controller unit adapted toreceive a signal from the silo air sensor and to control the flow of theheat transfer fluid from the heat transfer fluid storage tank inresponse to the signal.

The system may additionally comprise a valve controlling the flow ofheat transfer fluid to said evacuated tube solar panel from said heattransfer fluid storage tank and an evacuated tube solar panel sensoradapted to determine whether the evacuated tube solar panel is at atemperature sufficient to maintain the heat transfer fluid at apre-determined temperature and, in such condition, to signal thecontroller unit to initiate the flow of the heat transfer fluid from theheat transfer fluid storage tank to the evacuated tube solar panel.

The system may additionally comprise a valve controlling the flow ofheat transfer fluid to the at least one heat exchanger from the heattransfer fluid storage tank and wherein the silo air sensor is adaptedto determine whether the heat transfer fluid supplied to the heatexchanger by the heat transfer fluid storage tank is at a temperatureinsufficient to maintain the forced drying air at a pre-determinedtemperature and, in such event, to signal the heat transfer fluidstorage tank to supply heat transfer fluid to the at least one heatexchanger.

The silo air sensor may also be adapted to determine whether the forceddrying air is at a pre-determined temperature, and in the even it isnot, to signal the heat transfer fluid storage tank to supply heattransfer fluid to the at least one heat exchanger

As an optional feature, the system may additionally include a heattransfer fluid storage tank sensor adapted to determine whether the heattransfer fluid in the heat transfer fluid storage tank is at atemperature insufficient to maintain drying air in the plenum within thesilo at a pre-determined temperature and, in such event, to signal thecontroller unit to turn on electricity from the photovoltaic solar panelto the heating unit to heat the heat transfer fluid; or, optionally inthe alternative, if such condition is not present, to allow thephotovoltaic solar panel to provide energy to the local electricitygrid.

In a further optional embodiment, the system may additionally beconnected to a local electricity grid, and the photovoltaic solar panelmay be adapted to supply electricity alternatively to the heating unitand to the local electricity grid, and wherein the heat transfer fluidstorage tank sensor is adapted to determine whether the heat transferfluid in the heat transfer fluid storage tank is at a temperaturesufficient to maintain the drying air in the plenum within the silo at apre-determined temperature and, in such event, to signal the controllerunit to cause the photovoltaic solar panel to supply electricity to thelocal electricity grid.

The system may also include an air recirculation conduit adapted toaccept air from the interior space of the silo from a relatively higheroutput position, and to provide a flow of drying air into the interiorspace of the silo from a relatively lower input position through the airblower disposed in the air conduit and adapted to provide forced dryingair through the air conduit.

In those variations of the invention additionally featuring radiantheating in the silo floor, the silo may additionally comprise: (i) atleast one lateral wall and a roof; and (ii) a floor portion, the floorportion comprising: (1) a base of an insulative material; (2) anaggregate floor laid above the base and in heat transfer contact with aplenum within the silo, and (3) a radiant heating conduit adapted toaccept heat transfer fluid from the heat transfer fluid storage tank. Itis preferred that this embodiment additionally include a valvecontrolling the flow of heat transfer fluid to the radiant heatingconduit from the heat transfer fluid storage tank, and a radiant heatingconduit sensor adapted to determine whether the heat transfer fluidsupplied to the radiant heating conduits by the heat transfer fluidstorage tank is at a temperature insufficient to maintain drying air inthe plenum within the silo at a pre-determined temperature and, in suchevent, to signal the controller unit to open the valve to allow the heattransfer fluid to flow through the radiant heating conduit.

It is preferred that the controller unit is adapted to determine whetherthe heat transfer fluid supplied to the heat exchanger by the heattransfer fluid storage tank is at a temperature insufficient to maintainthe forced air at a pre-determined temperature and, in such event, tosignal the photovoltaic solar panel adapted to supply electricity to theheat transfer fluid storage tank heat transfer fluid storage tank tosupply the heat transfer fluid to the heat exchanger.

Although described herein as a system wherein the heat transfer fluidstorage tank is placed between the evacuated tube solar panel and theheat exchanger, other embodiments may include the use of a separate heattransfer fluid storage tank and evacuated tube solar panel, withindividual conduits and valves adapted to provide alternative flow asneeded to the heat exchanger(s), depending upon conditions.

The system may also be connected to a local electricity grid, such thatthe photovoltaic solar panel is adapted to supply electricityalternatively to supply electricity to the heat transfer fluid storagetank and to the local electricity grid.

As used herein, controller unit may be provided with a microprocessor toaccept and analyze feedback signals, and to initiate control signals asdescribed herein, in order to carry out the many required or optionalfunctions described herein. Such a microprocessor may be provided withprogrammed logic instructions to perform the feedback analysis functionsand control functions described herein. As may be appreciated by thoseof ordinary skill, the feedback and control features of the presentinvention may be carried out by any of a wide variety of means,including the use of varying assay points within the system, the use ofequivalent system parameters, ranges and thresholds, etc.

A Method of Drying Using Alternative Heat Transfer Fluid Sources

The present invention also includes a method for drying a particulateagricultural product in a silo, the method comprising: (a) placing aparticulate agricultural product in a silo having an interior space, thesilo comprising an air conduit adapted to circulate drying air withinthe interior space; (b) operating an air blower adapted to provideforced air into the air conduit, the air blower having a heat exchangerin heat transfer contact with the air conduit, the heat exchangeradapted to accept a heat transfer fluid; (c) providing a heat transferfluid to the heat exchanger, the heat exchanger being provided with theheat transfer fluid from a heat transfer fluid storage tank adapted toaccept and store a heat transfer fluid, the heat transfer fluid storagetank dispensing heat transfer fluid to the heat exchanger alternativelyby: (i) the heat transfer fluid storage tank comprising a heating unit,the heating unit heating the heat transfer fluid using electricitygenerated by a photovoltaic solar panel, and dispensing the heattransfer fluid to the heat exchanger; or (ii) the heat transfer fluidstorage tank accepting heat transfer fluid from an evacuated tube solarpanel adapted to heat the heat transfer fluid, and dispensing the heattransfer fluid to the heat exchanger; and (d) operating the blower andcontinuing to circulate drying air at sufficient temperature within theinterior space and for sufficient time so as to reduce the moisturecontent of the particulate agricultural product.

The method may optionally additionally comprise determining whether theheat transfer fluid supplied to the heat exchanger by the evacuated tubesolar panel is at a temperature insufficient to maintain the forced airat a pre-determined temperature, and in such event to signal the heattransfer fluid storage tank to supply the heat transfer fluid to theheat exchanger.

Also optional is the additional step of determining whether theelectricity is required to maintain the heat transfer fluid at apredetermined temperature and, in the event it is not, alternativelysupplying electricity to a local electricity grid.

Silo Design for Grain Drying System with Recirculation System andRadiant Floor

Another preferred system of the present invention is a system for dryinga particulate agricultural product in a silo, the system comprising: (a)a silo having an interior space, the silo comprising: (i) at least onelateral wall and a roof; (ii) a floor portion, the floor portioncomprising: (1) a base of an insulative material; (2) an aggregate floorlaid above the base, and (3) a radiant heating conduit; (b) an airrecirculation conduit adapted to accept air from the interior space ofthe silo from a relatively higher output position, and to provide a flowof air into the interior space of the silo from a relatively lower inputposition; (c) an air blower in the air recirculation conduit adapted toprovide forced air through the air recirculation conduit; and (d) atleast one heat exchanger in the air recirculation conduit and in heattransfer contact with the forced air, the heat exchanger adapted toaccept a heat transfer fluid.

The system may preferably include an additional interior air conduitadapted to circulate drying air within the interior space, such as inthe form of a perforated stirring bar.

It is also preferred that there be a first heat exchanger disposedupstream of the blower and a second heat exchanger disposed downstreamof the blower.

The system optionally includes a thermal collector such as an evacuatedtube solar panel adapted to heat a heat transfer fluid and to supply theheat transfer fluid to the at least one heat exchanger. It is alsopreferred that the thermal collector, such as an evacuated tube solarpanel, be adapted to heat a heat transfer fluid and to supply the heattransfer fluid to the radiant heating conduits.

The heat transfer fluid storage tank may be adapted to accept and storea heat transfer fluid, and to supply the heat transfer fluid to the heatexchanger, and an evacuated tube solar panel may be provided to heat aheat transfer fluid and to supply the heat transfer fluid alternativelyto the heat exchanger and to the heat transfer fluid storage tank, aswell as optionally to the radiant heating conduits.

It is also preferred that the system additionally includes aphotovoltaic solar panel adapted to generate electricity and to supplyelectricity to the heat transfer fluid storage tank, a heating unitadapted to heat the heat transfer fluid in the heat fluid storage tank,the heating unit adapted to use electricity generated by thephotovoltaic solar panel; and a controller unit adapted to determinewhether the heat transfer fluid supplied to the heat exchanger by theevacuated tube solar panel is at a temperature insufficient to maintainthe forced air at a pre-determined temperature, and in such event tosignal the heat transfer fluid storage tank to supply the heat transferfluid to the heat exchanger. The controller unit preferably is adaptedto determine whether the heat transfer fluid supplied to the heatexchanger by the heat transfer fluid storage tank is at a temperatureinsufficient to maintain the forced air at a pre-determined temperature,and in such event to signal the photovoltaic solar panel adapted tosupply electricity to the heat transfer fluid storage tank to supply theheat transfer fluid to the heat exchanger.

The photovoltaic solar panel may be adapted to supply electricityalternatively to supply electricity to the heat transfer fluid storagetank and to the local electricity grid.

In a preferred embodiment, the present invention provides a cropparticulate (grain) drying system utilizing solar energy to heat a heattransfer fluid or solution within concomitant forced-air and radiantheat systems which pass heated air through a crop particulate (grain)material contained within a conventional crop silo (bin) adjacent to aservice structure housing these systems. Solar thermal energy isharnessed by an evacuated (glass) tube solar thermal panel andtransferred to a fluid solution contained within a mechanical pipingsystem. This thermal energy is exchanged to the forced-air and radiantheat systems via the thermal storage and transmission tank. Forced-airis heated via fan coils and delivered to an under floor air plenumwithin the crop silo (bin) situated upon a concrete foundation heated bya radiant heat loop. This heated air is passed through a perforatedfloor and through the crop particulate material. Air is re-circulatedvia return air duct, continuously or intermittently (based upontemperature and humidity demands). Vents within the crop silo (bin)allow ambient air to be introduced to the system. Systems are used incombination to increase efficiencies and lessen or eliminate demand forexternal sources of energy. The crop storage itself is utilized as acontributing element within the network of systems, increasingefficiency and reducing energy losses. Excess heat and, or electricitymay be used to meet other on-site demands for these resources.

Electricity demand is met through utilization of solar photovoltaicpanels backed up by connection to an external power source (i.e. powerutility). Battery backup and, or an engine-driven generator may be usedto supplant connection to the electrical grid. Other renewable energysources such as wind energy or biomass could be utilized to meet on-sitedemand, especially in remote geographies without easy access to energyutilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a system for drying grain using solarenergy in accordance with one embodiment of the present invention.

FIG. 2 is a general schematic of a system for drying grain using solarenergy in accordance with one embodiment of the present invention.

FIG. 3 is a schematic of a heat transfer fluid and passive solar portionof a system for drying grain using solar energy in accordance with oneembodiment of the present invention.

FIG. 4 is a schematic of an air conduit and heat exchanger portion of asystem, with optional radiant silo heating, for a system for dryinggrain using solar energy in accordance with one embodiment of thepresent invention.

FIG. 5 is a detailed elevation view of a silo and air conduit, withoptional radiant silo heating, for a system for drying grain using solarenergy in accordance with one embodiment of the present invention.

FIG. 6 is a detailed plan view of a silo floor with optional radiantheating, for a system for drying grain using solar energy in accordancewith one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the foregoing summary, the following provides adetailed description of the preferred embodiment, which is presentlyconsidered to be the best mode thereof.

FIGS. 1-6 may be understood through reference to the following numeralsindicating the associated components and features throughout, andwherein such numerals refer to the same components and featuresthroughout the Figures.

-   -   0. service structure    -   1. solar photovoltaic panels    -   2. DC power lines (±)    -   3. solar PV disconnect    -   4. AC/DC power inverter    -   5. AC power utility disconnect    -   6. AC power lines    -   7. AC smart meter    -   8. electrical service panel    -   9. grounding    -   10. AC electrical feed to solar thermal system    -   11. AC electrical feed to forced-air and radiant heating systems    -   12. solar thermal temperature and pump controller    -   13. sensor wire to solar thermal panel temperature sensor    -   14. solar thermal panel temperature sensor    -   15. sensor wire to thermal storage and transfer tank temperature        sensor    -   16. thermal storage and transfer tank temperature sensor    -   17. AC electrical feed to solar thermal heat transfer fluid        circulating pump    -   18. solar thermal heat transfer fluid circulating pump    -   19. AC electrical feed to supplementary heating element    -   20. supplementary heating element    -   21. evacuated (glass) tube solar thermal panel    -   22. heat transfer fluid return line    -   23. expansion tank    -   24. in-line check valve    -   25. isolation valve    -   26. thermal storage and transfer tank (system filled with a heat        transfer fluid)    -   27. pressure relief valve    -   28. drain-down and fill valve    -   29. heat transfer fluid supply line to solar thermal panel    -   30. heat exchangers    -   31. fan and pump controller for air and radiant heating systems    -   32. sensor wire to crop silo (bin) humidistat-thermostat    -   33. humidistat-thermostat    -   34. AC electrical feed to fan coil heat transfer fluid        circulating pump    -   35. fan coil heat transfer fluid circulating pump    -   36. AC electrical feed to radiant heat transfer fluid        circulating pump    -   37. radiant heat transfer fluid circulating pump    -   38. AC electrical feed to fan (air handling unit)    -   39. fan (air handling unit)    -   40. heat transfer fluid supply line to fan coils    -   41. thermometer    -   42. flow meter    -   43. fan coils    -   44. heat transfer fluid return line from fan coils    -   45. heat transfer fluid supply line to radiant heat loop    -   46. radiant heat loop    -   47. heat transfer fluid return line from radiant heat loop    -   48. supply air (insulated) duct    -   49. manual air volume damper    -   50. supply air outlet    -   51. air plenum    -   52.(a) return air inlet    -   52.(b) alternate location    -   53. return air (insulated) duct    -   54. air filter    -   55. rigid insulation    -   56. concrete slab    -   57. perforated floor    -   58. crop silo (bin)    -   59. fill hatch and air vent    -   60. crop particulate material (grain, legumes, etc.)

FIG. 1 is a side perspective view of a system for drying grain usingsolar energy in accordance with one embodiment of the present invention.FIG. 1 shows an elevation view of a system in accordance with oneembodiment of the present invention that may be comprise the majorelements in a crop particulate (grain) drying system utilizing anevacuated (glass) tube solar thermal heating system 21 in conjunctionwith a solar photovoltaic electrical system comprising solarphotovoltaic panels. An optional service structure 0 housing mechanicalequipment supplies radiant heating fluid (such as in an housed tank, notshown, see thermal storage and transfer tank 26 described in FIG. 3, forreceiving heated heat transfer fluid from evacuated (glass) tube solarthermal panel 21) and heated air to a crop silo (or bin) 58.

For the purpose of directly heating the heat transfer fluid, any thermalcollectors appropriate to the desired application may be used. There arebasically three types of thermal collectors: flat-plate, evacuated-tube,and concentrating. A flat-plate collector, the most common type, is aninsulated, weatherproofed box containing a dark absorber plate under oneor more transparent or translucent covers. Evacuated-tube collectors aremade up of rows of parallel, transparent glass tubes. Each tube consistsof a glass outer tube and an inner tube, or absorber, covered with aselective coating that absorbs solar energy well but inhibits radiativeheat loss. The air is withdrawn (“evacuated”) from the space between thetubes to form a vacuum, which eliminates conductive and convective heatloss. Concentrating collector applications are usually parabolic troughsthat use mirrored surfaces to concentrate the sun's energy on anabsorber tube (called a receiver) containing a heat-transfer fluid. Theevacuated (glass) tube solar panels are preferred and may be thosedescribed in WO 2008/122968 A1, U.S. Pat. Nos. 6,819,465; 6,473,220, inU.S. Published Patent Applications Serial Nos. 20100065044 (all of whichare incorporated herein by reference), or otherwise commerciallyavailable from Kingspan Solar Inc. of Jessup, Md., Thermo Technologiesof Columbia, Md., and Viessmann Werke of Allendorf, Germany.

Other collectors include those described in U.S. Published PatentApplications Serial Nos. 20100065104, 20090025709, 20090223550 and20080216823 (all of which are incorporated herein by reference).

In a preferred embodiment, FIG. 1 also shows silo (or bin) 58 which maybe placed upon concrete slab 56, and is preferably provided with fillhatch and air vent 59 and humidistat/thermostat 33. Also shown is returnair (insulated) duct 53 that is serviced by a return inlet 52(a) (seeFIG. 5) that may be in an alternate location 52(b).

Figure is a schematic illustration of a solar photovoltaic electricalsystem in relation to on-site electrical loads 10 and an external powerutility. FIG. 2 shows the arrangement and cooperation of severalcomponents of the system of the present invention. FIG. 2 shows solarenergy incident upon solar photovoltaic panels 1 from which DC powerlines (±) 2 conduct electricity to solar PV disconnect 3 which isgrounded at grounding point 9 a. Solar PV disconnect 3 is furtherconnected to AC/DC power inverter 4 which supplies AC smart meter 7 withAC current via AC power line 6 a, which in turn is connected to AC powerutility disconnect 5 and electrical service panel 8 via AC power lines 6b and 6 c, respectively. AC power utility disconnect 5 and electricalservice panel 8 also preferably have individual ground points 9 b and 9c, respectively. AC power utility disconnect 5 is also adapted toreceive electric power, such as from the local power utility, as needed.Electrical service panel 8 in turn supplies electric power to ACelectrical feed 10 to solar thermal system, and to AC electrical feed 11to forced-air and radiant heating systems 11, as needed. The ACelectrical feed to solar thermal system 10 preferably is used to heat astorage tank of heat transfer fluid as a heat source back up in theevent the thermal collector system fails to provide sufficient energy tothe heat exchanger(s) associated with the air inlet as described herein.

FIG. 3 is a schematic illustration of an evacuated (glass) tube solarthermal heating system containing a fluid utilized to transfer heat viaheat exchangers 30 to a heating fan coil (air) system and radiantheating system.

FIG. 3 shows evacuated (glass) tube solar thermal heating system 21connected to heat transfer fluid return line 22 which proceeds throughin-line check valve 24 and isolation valve 25 a to thermal storage andtransfer tank 26 (system filled with a heat transfer fluid). Optionally,an expansion tank 23 may be provided as shown. FIG. 3 also shows heatexchangers 30 with heat transfer fluid supply line 40 to fan coils 43(see FIG. 4), heat transfer fluid return line 44 from fan coils 43, heattransfer fluid supply line 45 to radiant heat loop 46, and heat transferfluid return line 47 from radiant heat loop 46. FIG. 3 also shows thepressure relief valve 27 and drain-down and fill valve 28 serving tank26. The thermal storage and transfer tank 26 typically will be providedwith heat transfer fluid supply line 29 to return heat transfer fluid tosolar thermal panel 21. This fluid supply line 29 is governed byisolation valve 25 b, solar thermal heat transfer fluid circulating pump18 and isolation valve 25 c. Solar thermal heat transfer fluidcirculating pump 18 may be serviced by AC electrical feed 17 from solarthermal temperature and pump controller 12 so as to be adapted to pumpreturn solar thermal heat transfer fluid to solar thermal panel 21.

Solar thermal temperature and pump controller 12 may also be connectedby a sensor wire to solar thermal panel temperature sensor 14 to monitorthe temperature of the fluid in the solar thermal panel 21, in order todetermine whether AC power is required to be supplied to the thermalstorage and transfer tank 26 for supplementary heating from the ACelectrical feed 10. The solar thermal temperature and pump controller 12is also signaled by sensor wire 15 which monitors the temperature of tothermal storage and transfer tank via thermal storage and transfer tanktemperature sensor 16. This sensor monitors the temperature of the hattransfer fluid to determine whether the heat transfer fluid requiressupplementary heating if it is not being kept within the desiredtemperature range or at a given threshold by the fluid from the solarthermal panel 21. If not, the solar thermal temperature and pumpcontroller 12 may control the system by supplying supplementary heating.Thermal storage and transfer tank 26 may also be provided withsupplementary heating element 20 which is adapted to be served by ACelectrical feed 19 from solar thermal temperature and pump controller12. Solar thermal temperature and pump controller 12 receives an ACelectrical feed 10 for the solar thermal system.

Typically and preferably, thermal storage and transfer tank temperaturesensor 16 determines whether the fluid in the thermal storage andtransfer tank is at sufficient temperature to provide sufficient heat tothe heat exchangers to heat the drying air to the desired temperature(typically 140-200 F, preferably about 170 F) and, if not, to causefluid from the solar thermal panel to be brought into the thermalstorage and transfer tank to increase the overall temperature of thefluid in the thermal storage and transfer tank. In addition, it ispreferred that the sensors and controller also determine that there issufficient differential between the temperature of the fluid in thethermal storage and transfer tank and the fluid in the solar thermalpanel to prevent/defeat fluid transfer in the event the fluid in thesolar thermal panel is not yet at sufficient temperature to increase theoverall temperature of the fluid in the thermal storage and transfertank. Thus, the solar thermal panel temperature sensor 14 and thermalstorage and transfer tank temperature sensor 16 outputs are coordinatedby the controller to assure that effective fluid transfer is made toincrease the overall temperature of the fluid in the thermal storage andtransfer tank, as the system requires.

Through this arrangement, heat transfer fluid may be supplied to theheat exchanger system as described in FIG. 4. The availability of theheat transfer fluid allows for the continuous effective operation of thegrain drying system, whether during times of effectively high sunlightor during periods where the passive solar panels do not providesufficient energy to the heat exchangers, in which case the heattransfer is actively heated by energy from the photovoltaic panels.

The humidistat-thermostat 33 monitors air plenum 51 of silo 58 andprovides control feedback through sensor wire 32 to fan and pumpcontroller 31 which governs the flow of air through conduit 53 by fan39, and the flow of heat transfer fluid into the heat exchanger systemas described herein. The AC electrical feed 11 supplies AC power toforced-air and radiant heating system fan and pump controller 31. Thecontroller 31 is adapted to the heat transfer fluid supplied to the heatexchanger by the heat transfer fluid storage tank is at a temperatureinsufficient to maintain the forced air at a pre-determined temperature,and in such event to signal the photovoltaic solar panel adapted tosupply electricity to the heat transfer fluid storage tank heat transferfluid storage tank to supply the heat transfer fluid to the heatexchanger.

The system may be used in conjunction with a local electricity grid,with the photovoltaic solar panel being adapted to supply electricityalternatively to supply electricity to the heat transfer fluid storagetank and to the local electricity grid.

FIG. 4 is a schematic illustration of mechanical systems supplyingheated air to a crop silo (bin) 58 via an air handling unit (i.e., fan39) blowing air through heating fan coils 43 within a ducted system. Fan39 receives control signals from fan and pump controller 31 for the airand radiant heating systems, and this control system in turn provides ACelectrical feed 38.

FIG. 4 shows air conduit 53, which in this embodiment is an insulatedreturn air duct from the upper portion of silo 58 as shown in FIG. 1.This conduit contains fan 39 and two heat exchangers 43, as well asoptional air filter 54. The heat exchangers 43 receive heat transferfluid from heat transfer fluid supply line 40 governed by isolationvalves 25 d, as well as thermometer 41 a and flow meter 42 a that serveto provide feed back control upon the in-coming heat transfer fluidflow. Also shown in heat transfer fluid supply line 40 is drain-down andfill valve 28 a, and fan coil heat transfer fluid circulating pump 35that receives control signals from fan and pump controller 31 governingthe air and radiant heating systems, which in turn provides ACelectrical feed 34 to fan coil heat transfer fluid circulating pump. Fancoil heat transfer fluid circulating pump 35 is also preferably providedwith isolation valves 25 e.

The heat exchangers 43 release heat transfer fluid from heat transferfluid heat transfer fluid return line 44 governed by isolation valves 25f, as well as thermometer 41 b and flow meter 42 b that serve to providefeed back control over the out-going heat transfer fluid flow. Alsoshown in heat transfer fluid return line 44 is in-line check valve 24 aand downstream isolation valve 25 g.

In addition, a radiant heating system circulates heat transfer fluidthrough a radiant heat loop 46 underneath same crop silo (bin) 58 viaheat transfer fluid supply return lines 45 and 47. The radiant heat loop46 receives heat transfer fluid from heat transfer fluid supply line 45which is provided with thermometer 41 c and flow meter 42 c that serveto provide feed back control upon the in-coming heat transfer fluidflow. Also shown in heat transfer fluid supply line 45 is drain-down andfill valve 28 b, and fan coil heat transfer fluid circulating pump 37that receives control signals from fan and pump controller 31 governingthe air and radiant heating systems, which in turn provides ACelectrical feed 36 to fan coil heat transfer fluid circulating pump.Radiant heat loop heat transfer fluid circulating pump 37 is alsopreferably provided with isolation valves 25 h.

Radiant heat loop 46 releases heat transfer fluid from heat transferfluid heat transfer fluid return line 47 governed by check valve 24 band isolation valve 25 i, as well as thermometer 41 d and flow meter 42d that serve to provide feed back control over the out-going heattransfer fluid flow.

FIG. 4 also shows the position of insulated supply air duct 48 andmanual air volume damper 49.

FIG. 5 is a cross-sectional view (not-to-scale) depicting thetransmission of heated air to a crop silo (bin) 58 via both a forced-airsystem and a radiant heating system associated therewith. The heat isproduced by a solar thermal heating system in conjunction with a solarphotovoltaic electrical system and is transmitted to the cropparticulate material 60 via an under floor air plenum 51 situated over aconcrete slab 56 heated by a radiant heat loop 46 isolated from heatloss to the earth by rigid insulation 55. FIG. 5 shows a detailed viewof the interior of silo 58, showing insulated supply air duct 48 andmanual air volume damper 49 connecting the air conduit 53 to the airplenum 51. This view also shows an alternative location of return airinlet 52 b. FIG. 5 also shows the perforated floor 57 through which thewarmed air flow proceeds to contact the grain, such as a cropparticulate material (grain, legumes, etc.) above this point. FIG. 5also shows the direction of the air flow through a drying zone to a wetzone and further into return air conduit 52 a, or exiting through fillhatch/air vent 59. The temperature of the air in the plenum 51 isfurther maintained by action of the radiant heating system heating floorthat may include rigid insulation 55 and concrete or aggregate slab 56.

FIG. 5 is a schematic illustration of mechanical systems supplyingheated air to a crop silo (bin) 58 via an air handling unit (fan) 39blowing air through heating fan coils 43 within a ducted system. Inaddition, a radiant heating system circulates heat transfer fluidthrough a radiant heat loop 46 underneath same crop silo (bin) 58 viaheat transfer fluid supply/return lines 45 and 47.

FIG. 6 shows a detailed plan view of radiant heat loop underneath theconcrete slab 56. The exact sizing may be different for each system,depending upon volume and heat capacity of each system. Typically, theradiant tubing is oxygen-barrier ½ inch pex tubing. FIG. 6 shows theloop in plan view. The tubing normally will be spaced at about 8 inches,again depending upon the typical ground temperature and the desiredoperating temperature of the air flow. In a preferred embodiment, theaggregate underlayment (base) for the concrete slab would be underneatha layer of rigid insulation. In this way, the concrete slab 56 is usedas a thermal mass for heat storage and transmission in a configurationas shown.

It is apparent that while specific embodiments of the invention aredisclosed, various modifications to the apparatus or parameters of theprocess may be made which will be within the spirit and scope of theinvention. Therefore, the spirit and scope of the present inventionshould be determined by reference to the claims below.

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 10. (canceled) 11.A system for drying a particulate agricultural product in a silo, saidsystem comprising: b. a silo having an interior space, said silocomprising: i. at least one lateral wall and a roof; ii. a floorportion, said floor portion comprising:
 1. a base of an insulativematerial; and
 2. an aggregate floor laid above said base, and
 3. aradiant heating conduit.
 12. A system according to claim 11,additionally comprising: b. a heat transfer fluid storage tank adaptedto accept and store a heat transfer fluid, and to supply said heattransfer fluid to said radiant heating conduit and to receive said heattransfer fluid from said radiant heating conduit; c. a silo air sensoradapted to determine whether said drying air is at a predeterminedtemperature; and d. a controller unit adapted to receive a signal fromsaid silo air sensor and to control the flow of said heat transfer fluidfrom said heat transfer fluid storage tank to said radiant heatingconduit in response to said signal.
 13. A system according to claim 11,additionally comprising: b. a heat transfer fluid storage tank adaptedto accept and store a heat transfer fluid, and to supply said heattransfer fluid to said radiant heating conduit and to receive said heattransfer fluid from said radiant heating conduit; c. an evacuated tubesolar panel adapted to heat a heat transfer fluid and to supply saidheat transfer fluid to said heat transfer fluid storage tank and toreceive said heat transfer fluid from said heat transfer fluid storagetank; d. a photovoltaic solar panel adapted to generate electricity andto supply electricity to said heat transfer fluid storage tank; e. aheating unit adapted to heat the heat transfer fluid in said heat fluidstorage tank, said heating unit adapted to use electricity generated bysaid photovoltaic solar panel; f. a silo air sensor adapted to determinewhether said drying air is at a predetermined temperature; and g. acontroller unit adapted to receive a signal from said silo air sensorand to control the flow of said heat transfer fluid from said heattransfer fluid storage tank to said radiant heating conduit in responseto said signal.
 14. A method for drying a particulate agriculturalproduct in a silo, said method comprising: a. placing a particulateagricultural product in a silo having an interior space, said silocomprising an air conduit adapted to provide drying air to said interiorspace; b. operating an air blower adapted to provide forced air intosaid air conduit, said air blower having a heat exchanger in heattransfer contact with said air conduit, said heat exchanger adapted toaccept a heat transfer fluid; c. providing a heat transfer fluid to saidheat exchanger, said heat exchanger being provided with said heattransfer fluid from a heat transfer fluid storage tank adapted to acceptand store a heat transfer fluid, said heat transfer fluid storage tankdispensing heat transfer fluid to said heat exchanger alternatively by:i. said heat transfer fluid storage tank comprising a heating unit, saidheating unit heating said heat transfer fluid using electricitygenerated by a photovoltaic solar panel, and dispensing said heattransfer fluid to said heat exchanger; or ii. said heat transfer fluidstorage tank accepting heat transfer fluid from an evacuated tube solarpanel adapted to heat said heat transfer fluid, and dispensing said heattransfer fluid to said heat exchanger; and d. operating said blower andcontinuing to circulate drying air at sufficient temperature within saidinterior space and for sufficient time so as to reduce the moisturecontent of said particulate agricultural product.
 15. A method accordingto claim 14, wherein said silo comprises a floor portion comprising aradiant heating conduit and said heat transfer fluid storage tank isfurther adapted to supply said heat transfer fluid to said radiantheating conduit, said method additionally comprising dispensing saidheat transfer fluid to said radiant heating conduit in step (ii).
 16. Amethod according to claim 14, wherein said silo is part of a graindrying system that additionally comprises a photovoltaic solar paneladapted to generate electricity and to supply electricity, a heatingunit adapted to heat the heat transfer fluid in said heat fluid storagetank, said heating unit adapted to use electricity generated by saidphotovoltaic solar panel; said method additionally comprising, andduring step (c), determining whether said heat transfer fluid suppliedto said heat exchanger by said heat transfer fluid storage tank is at atemperature insufficient to maintain said forced drying air at apre-determined temperature, and in such event to signal saidphotovoltaic solar panel to supply electricity to said heat transferfluid storage tank.
 17. A method according to claim 16, wherein saidsilo is part of a grain drying system that additionally comprises aphotovoltaic solar panel adapted to generate electricity and to supplyelectricity, a heating unit adapted to heat the heat transfer fluid insaid heat fluid storage tank, said heating unit adapted to useelectricity generated by said photovoltaic solar panel, saidphotovoltaic solar panel connected to a local electricity grid; saidmethod additionally comprising, and during step (c), determining whethersaid heat transfer fluid supplied to said heat exchanger by said heattransfer fluid storage tank is at a temperature sufficient to maintainsaid forced drying air at a pre-determined temperature, and in suchevent to signal said photovoltaic solar panel to supply electricity tosaid local electricity grid.